Don't know why I didn't think of this earlier, if you're really concerned about who signs up to your forum - you could always go with the Manual Validation option, see "Setup", "Users".
Then you'd be the one to validate each user. It would allow you to see their e-mail address, dialog with them in some fashion if desired, and then validate them.
It's a lot of work though.
Then you'd be the one to validate each user. It would allow you to see their e-mail address, dialog with them in some fashion if desired, and then validate them.
It's a lot of work though.